How do I install the Bench Virtual Rule skill?

Run npx skillmds@latest add markuplint/bench-virtual-rule in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Bench Virtual Rule safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Bench Virtual Rule?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Bench Virtual Rule free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Bench Virtual Rule?

markuplint (@markuplint) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Bench Virtual Rule by markuplint — Agent Skill

Name: Bench Virtual Rule
Author: markuplint

Bench Virtual Rule

Mirror a preset virtual rule (selectors under `nodeRules` in preset.html-standard.jsonc and similar) into bench/config.ts so the benchmark exercises it. Use when a new disallowed-element / similar selector lands in a preset and the matching nu fixtures remain stuck at nu-only despite the new rule existing in markuplint. Trigger keywords: virtual rule, nodeRules, disallowed-element, preset html-standard, bench config mirror, rule does not fire on bench, preset rule not exercised.

markuplint 4bf63c2 2.2 KB Updated Sep 17, 2026

File contents

Bench Virtual Rule Mirror Skill

bench/config.ts does not extends: ['markuplint:html-standard']. It curates rules explicitly so the bench surface stays scoped to nu-validator capability. Consequence: any new entry in a preset's nodeRules[] is invisible to the benchmark until the same selectors are mirrored into bench/config.ts. Symptom: fixtures the new virtual rule should detect remain at nu-only and look like a markuplint coverage gap when the rule already exists.

Procedure

Add the selector(s) to the relevant preset (preset.html-standard.jsonc or similar).
Mirror the same selectors into bench/config.ts nodeRules[] with a comment naming the source preset rule (e.g. // Mirrors html-standard/no-duplicate-charset).
Run yarn bench:update:ml.
Verify the target fixtures flipped from nu-only → match-error. If they didn't, the selectors don't actually match those fixtures — check selector syntax (caveats below).
If the rule does not map onto any nu-validator capability, skip step 2 and add a // not mirrored: <reason> comment to the preset rule's JSDoc so the next maintainer knows it was a conscious decision.

Selector caveats

HTML attribute names are matched ASCII case-insensitively ([charset] matches <meta CHARSET>). Use lowercase to match HTML's normative form.
The i flag (e.g. [name="description" i]) only applies to attribute values — it is unnecessary for the name, which is already case-folded for HTML.
Sibling selectors (~) only match elements after the anchor. Coexistence-style constraints typically need both directions (a ~ b and b ~ a) so the rule fires regardless of source order.

---name: bench-virtual-ruledescription: Mirror a preset virtual rule (selectors under `nodeRules` in preset.html-standard.jsonc and similar) into bench/config.ts so the benchmark exercises it. Use when a new disallowed-element / similar selector lands in a preset and the matching nu fixtures remain stuck at nu-only despite the new rule existing in markuplint. Trigger keywords: virtual rule, nodeRules, disallowed-element, preset html-standard, bench config mirror, rule does not fire on bench, preset rule not exercised.---# Bench Virtual Rule Mirror Skill`bench/config.ts` does **not** `extends: ['markuplint:html-standard']`.It curates rules explicitly so the bench surface stays scoped tonu-validator capability. Consequence: any new entry in a preset's`nodeRules[]` is invisible to the benchmark until the same selectorsare mirrored into `bench/config.ts`. Symptom: fixtures the newvirtual rule should detect remain at `nu-only` and look like amarkuplint coverage gap when the rule already exists.## Procedure1. Add the selector(s) to the relevant preset (`preset.html-standard.jsonc` or similar).2. Mirror the same selectors into `bench/config.ts` `nodeRules[]` with a comment naming the source preset rule (e.g. `// Mirrors html-standard/no-duplicate-charset`).3. Run `yarn bench:update:ml`.4. Verify the target fixtures flipped from `nu-only` → `match-error`. If they didn't, the selectors don't actually match those fixtures — check selector syntax (caveats below).5. If the rule does not map onto any nu-validator capability, skip step 2 and add a `// not mirrored: <reason>` comment to the preset rule's JSDoc so the next maintainer knows it was a conscious decision.## Selector caveats- HTML attribute *names* are matched ASCII case-insensitively (`[charset]` matches `<meta CHARSET>`). Use lowercase to match HTML's normative form.- The `i` flag (e.g. `[name="description" i]`) only applies to attribute *values* — it is unnecessary for the *name*, which is already case-folded for HTML.- Sibling selectors (`~`) only match elements after the anchor. Coexistence-style constraints typically need both directions (`a ~ b` *and* `b ~ a`) so the rule fires regardless of source order.

Frequently asked questions